Laser video projector having multi-channel acousto-optic modulator, and method and circuit for driving the same

ABSTRACT

Provided are a laser video projector having a multi-channel acousto-optic modulator, and a method and circuit for driving the laser video projector. The laser video projector includes a light generating portion, an optic modulator, an optic combining portion, and an optic scanning portion. The light generating portion emits light to be used to project a video image. The optic modulator modulates the light incident from the light generating portion by using the video signal. The optic combining portion combines modulated light beams emitted from the optic modulator. The optic scanning portion scans light incident from the optic combining portion on a screen. The optic modulator has six or more optic modulation channels so that a plurality of red light beams, a plurality of green light beams, and a plurality of blue light beams incident in a state suitable for optic modulation are simultaneously modulated. Accordingly, limitations in the performance of an optic modulator and an optic scanner can be overcome. Also, a laser video projector can be made small. In addition, the degree of freedom for arranging components increases and the components can be well arranged. Furthermore, a video image of high brightness can be realized.

This application claims the priority of Korean Patent Application No.2002-13256, filed on Mar. 12, 2002, in the Korean Intellectual PropertyOffice, the disclosure of which is incorporated herein in its entiretyby reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a laser video projector, and moreparticularly, to a laser video projector having a multi-channelacousto-optic modulator, and a method and circuit for driving the same.

2. Description of the Related Art

Lasers are used in various types of displays because of their opticalcharacteristics, e.g., a monochromatic characteristic having a linespectrum almost close to zero, a straightforward characteristic, acondensing characteristic, high brightness, and the like.

In a display, a laser can realize three times more natural colors than afluorescent substance. Also, when compared with a lamp, the laser cangreatly improve the optical conversion efficiency and reduce the powerconsumption necessary for obtaining the same brightness. Thus, heatgenerated in the display system can greatly decrease. In addition, in acase where the laser is used as a light source in a display, thelifetime of the light source can be 10,000 hours or more. Furthermore, avideo image having high brightness and high clearness can be realized ona large-scale screen using the high brightness of the laser.

FIG. 1 is a schematic view of a laser video projector, a kind of displayusing a laser as a light source. Here, reference numeral 900 denotes ascreen on which a video signal is projected. Reference numeral 850denotes a reflector plate which reflects the video image incident fromdownward to project the video image on the screen 900. Reference numeral750 denotes an optical engine which forms the video image and scans thevideo image onto the reflector plate 850.

As shown in FIG. 2, the optical engine 750 includes a plurality ofelements as well as a light source 100 which emits a white laser thatwill be used for forming the video image.

In detail, a first collimating lens 220, which changes the white laserto parallel laser light, is positioned in front of an emitting surfaceof the light source 100 that emits the white laser. A first highreflection mirror 210, which changes the optical path of the parallellaser light, is placed in front of the first collimating lens 220. Thefirst collimating lens 220 includes a plurality of lenses to correct thechromatic aberration of the parallel laser light. The first collimatinglens 220 and the first high reflection mirror 210 exist in the sameoptical path. The parallel laser light is incident on an opticalseparator 250 via the first high reflection mirror 210. The opticalseparator separates the parallel laser light into three monochromaticlight beams, i.e., a blue light beam B, a green light beam G, and a redlight beam R. The optical separator 250 has a first dichroic mirror 670a that separates the blue light beam B from the parallel laser light, asecond dichroic mirror 680 a that separates the green light beam G fromthe parallel laser light that passed through the first dichroic mirror670 a, and a second high reflection mirror 690 a that reflects the redlight beam R that passed through the second dichroic mirror 680 a tochange the optical path of the red light beam R. A first focusing lens640 a focuses the blue light beam B separated from the parallel laserlight by the first dichroic mirror 670 a on a first acousto-opticmodulator 610. A second focusing lens 650 a focuses the green light beamG separated by the second dichroic mirror 680 a on a secondacousto-optic modulator 620. A third focusing lens 660 a focuses the redlight beam R reflected by the second high reflection mirror 690 a on athird acousto-optic modulator 630. The red, green, and blue light beamsR, G, and B focused on the first, second, and third acousto-opticmodulators 610, 620, and 630 are modulated using an input video signal.The second, third, and fourth collimating lenses 640 b, 650 b, and 660 bin the rear of the first, second, and third acousto-optic modulators610, 620, and 630 make the blue, green, and red light beams B′, G′, andR′ modulated by the first, second, and third acousto-optic modulators610, 620, and 630 into parallel light beams like the red, green, andblue light beams R, G, and B which are not yet incident onto the first,second, and third focusing lens 640 a, 650 a, and 660 a. First, second,and third apertures A1, A2, and A3 are placed between the second, third,and fourth collimating lenses 640 b, 650 b, and 660 b and the first,second, and third acousto-optic modulators 610, 620, and 630. The first,second, and third apertures A1, A2, and A3 intercept components of themodulated light beams, emitted from the first, second, and thirdacousto-optic modulators 610, 620, and 630, deviating from optical axesof the second, third, and fourth collimating lenses 640 b, 650 b, and660 b from being incident on the second, third, and fourth collimatinglenses 640 b, 650 b, and 660 b. The first, second, and third aperturesA1, A2, and A3 are close to the second, third, and fourth collimatinglenses 640 b, 650 b, and 660 b, respectively. The modulated light beamsB′, G′, and R′ which passed through the second, third, and fourthcollimating lenses 640 b, 650 b, and 660 b are incident on an opticalcombiner 650 to combines the light beams B′, G′, and R′ into a lightbeam B′+G′+B′. When the modulated red light beam R′ reflected by a thirdhigh reflection mirror 690 b of the optical combiner 650 passes througha fourth dichroic mirror 680 b existing on the same optical path as thethird collimating lens 650 b, the modulated red light beam R′ iscombined to the modulated green light beam G′ reflected by the fourthdichroic mirror 680 b. The combined light beam G′+B′ is reflected by thethird dichroic mirror 670 b existing on the same optical path as thesecond collimating lens 640 b and combined with the modulated blue lightbeam B′ passing through the third dichroic mirror 670 b into the lightbeam R′+G′+B′. The light beam R′+G′+B′ is reflected by a fourth highreflection mirror 710 existing on the same optical path as the thirddichroic mirror 670 b so as to go toward a polygon mirror 800, which isa optical scanner having a plurality of reflection surfaces that arepositioned on the same plane as the fourth reflection mirror 710 toperiodically scan incident light in a given direction. The light beamR′+G′+B′ incident on the polygon mirror 800 is reflected by thereflection surfaces of the polygon mirror 800 and horizontally scanned.The light beam R′+G′+B′ passes through first and second relay lenses 310and 320 between the polygon mirror 800 and the galvanometer 700 and isfocused on a mirror surface 700 a of a galvanometer 700. The focusedlight beam R′+G′+B′ is vertically scanned by the mirror surface 700 a ofthe galvanometer 700. The horizontally and vertically scanning of thelight beam R′+G′+B′ results in forming a video image, which is reflectedby the reflector plate 850 shown in FIG. 1 and projected on the screen900.

In the above-described conventional laser video projector, theresolution of the video image projected on the screen 900 depends on thefirst, second, and third acousto-optic modulators 610, 620, and 630 andthe polygon mirror 800.

In general, the video signal processing performance of an acousto-opticmodulator (AOM) depends on the focusing intensity of a laser. Since thefocusing degree of the laser depends on the size of a laser beam,quality of the laser, and a focusing lens used, the laser is limited inbeing focused to more than predetermined degree. Thus, the conventionallaser video projector can process a video image corresponding to an XGAvideo signal. However, it is very difficult for the conventional laservideo projector to process the video image having a resolution higherthan XGA. Also, the number of horizontal scan lines scanned by thepolygon mirror 800 depends on the number of mirror surfaces of thepolygon mirror 800 and the rotating speed of the polygon mirror 800.However, since the conventional laser video projector has a limitationin increasing the number of mirror surfaces and the rotating speed, itis quite difficult for the conventional laser video project to process avideo image having a resolution higher than XGA.

In a case where a current MEMS scanner is used, the conventional laservideo projector has difficulty realizing a video having a resolutionhigher than the resolution of an XGA video image due to its operationalspeed.

As described above, it is difficult to obtain a video image having aresolution higher than that of an XGA video image by using theconventional laser video projector due to a limited performance of anacousto-optic modulator and an optical scanner.

SUMMARY OF THE INVENTION

Accordingly, the invention provides a laser video projector which canrealize a video image having a resolution higher than the resolution ofan XGA video image and whose size can be reduced.

The present invention provides a method for operating the laser videoprojector.

The present invention provides a circuit for driving the laser videoprojector.

According to an aspect of the present invention, there is provided alaser video projector including a light generating portion, an opticmodulator, an optic combining portion, and an optic scanning portion.The light generating portion emits light to be used to project a videoimage. The optic modulator modulates the light incident from the lightgenerating portion by using the video signal. The optic combiningportion combines modulated light beams emitted from the optic modulator.The optic scanning portion scans light incident from the optic combiningportion on a screen. The optic modulator has six or more opticmodulation channels so that a plurality of red light beams, a pluralityof green light beams, and a plurality of blue light beams incident in astate suitable for optic modulation are simultaneously modulated.

Here, the optic modulator includes first through third multi-channelacousto-optic modulators, each having at least two or more opticmodulation channels or includes one multi-channel acousto-opticmodulator having the at least six or more optic modulation channels.

The light generating portion includes a light source portion, a firstoptical path changing portion, first and second lighttransmission/reflection portions, a second optical path changingportion, first through third monochromatic separators, and first throughthird groups of lenses. The light source portion emits the light to beused to project the video image. The first optical path changing portionchanges an optical path of the light emitted from the light generatingportion. The first and second light transmission/reflection portionssequentially separate first and second monochromatic light beams fromthe light incident from the first optical path changing portion. Thesecond optical path changing portion changes an optical path of lightincident from the second light transmission/reflection portion. Thefirst through third monochromatic separators equally separate lightbeams incident from the first and second light transmission/reflectionportions and the second optical path changing portion as many as opticmodulation channels in the optic modulator. The first through thirdgroups of lenses correspond on a one-to-one basis to the first throughthird monochromatic separators to focus light beams incident from thefirst through third monochromatic separators on the channels in theoptic modulator.

At least one of the first through third monochromatic separators is atransmissible plate that equally separates light beams incident from thefirst and second light transmission/reflection portions and the secondoptical path changing portion by using an internal reflection process ofmulti-steps or includes first through fourth beam splitters.

According to another aspect of the present invention, the lightgenerating portion includes a light source portion that emits as manylaser light beams as the optic modulation channels in the opticmodulator, and groups of lenses that are positioned between the opticmodulator and the light source portion, correspond on a one-to-one basisto the optic modulation channels, and focus the emitted laser lightbeams on the optic modulation channels.

Here, the light generating portion further includes optic transmittersthat are placed between the light generating portion and the groups oflenses and transmit laser light beams emitted from the light generatingportion to the groups of lenses. The optic transmitters are as manyoptical fibers as laser light beams emitted from the light generatingportion.

The optic combining portion includes fourth through sixth groups oflenses, a third optical path changing portion, a third lighttransmission/reflection portion, and a fourth lighttransmission/reflection portion. The fourth through sixth groups oflenses change modulated light beams emitted from the optic modulator toparallel light beams. The third optical path changing portion changesoptical paths of light beams incident from the fourth group of lenses.The third light transmission/reflection portion reflects light beamsincident from the fifth group of lenses and transmits light beamsincident from the third optical path changing portion so that the lightbeams incident from the fifth group of lenses are combined with thelight beams incident from the third optical path changing portion. Thefourth light transmission/reflection portion reflects light beamsincident from the sixth group of lenses and transmits light beamsincident from the third light transmission/reflection portion so thatthe light beams incident from the sixth group of lenses are combinedwith the light beams incident from the third lighttransmission/reflection portion.

According to still another aspect of the present invention, the lightcoupling portion includes optic transmitters, first micro focusinglenses, and second micro focusing lenses. The optic transmitters combineand transmit modulated red, green, and blue laser light beams emittedfrom the optic modulation channels to the optic scanning portion. Thefirst micro focusing lenses are placed at ends of the optic transmittersto focus the modulated laser light beams emitted from the opticmodulation channels on the optic transmitters. The second micro focusinglenses are placed at the other ends of the optic transmitters so thatlight transmitted via the optic transmitters is incident on the opticscanning portion.

Here, the optic transmitters are optical fibers that are as many as theoptic modulation channels but reduce to ⅓ while advancing toward theoptic scanning portion.

The optic scanning portion includes a first focusing lens, a first opticscanner, a second optic scanner, a relay lens system, and a secondfocusing lens. The first focusing lens that focuses light beams incidentfrom the optic combining portion. The first optic scanner that reflectsthe light focused by the first focusing lens so that the light ishorizontally scanned on the screen. The second optic scanner determinesthe vertical position of the light reflected by the first optic scannerto scan the light on the screen. The relay lens system that is placedbetween the first and second optic scanners and focuses the lightreflected by the first optic scanner on the second optic scanner. Thesecond focusing lens is placed between the screen and the second opticscanner to control the vertical position of light projected on thescreen.

According to still yet another aspect of the present invention, thelaser video projector further includes a reflector plate that is placedabove the second optic scanner to project light reflected by the secondoptic scanner on the screen via the second focusing lens.

According to yet another aspect of the present invention, there is alsoprovided a method for driving a laser video projector including ananalog/digital converter that converts an analog video signal to adigital signal and a plurality of FIFO memories that are connected tothe analog/digital converter to write the digital signal. Here, videosignals read from the analog/digital converter are sequentially writtenin the plurality of FIFO memories, and the video signals are read fromthe plurality of FIFO memories when a video signal is written in thelast one of the plurality of FIFO memories.

Here, the video signals are read from the plurality of FIFO memories ata speed lower than a speed for writing the video signals in theplurality of FIFO memories.

According to yet another aspect of the present invention, there is alsoprovided a circuit for driving a laser video projector including ananalog/digital converter that converts an analog signal to a digitalsignal, a memory in which the analog signal is written, digital/analogconverters that convert video information read from the memory to analogsignals, and an optic modulator that modulates light by using the analogsignal read from the digital/analog converter. Here, the memory includesa plurality of FIFO memories in which video signals read from theanalog/digital converter are sequentially written, the number of thedigital/analog converters is equal to the number of the plurality ofFIFO memories, and the optic modulator includes as many optic modulationchannels as the plurality of FIFO memories.

According to the present invention, limitations in the performance ofthe optic modulator and the optic scanner can be overcome, and the laservideo projector can be made very small. Also, since components can bedisposed in predetermined positions due to optical fibers, the degree offreedom for arranging the components increases. In addition, since theoptical fibers can be easily arranged by using arrangement stages, thecomponents can be well arranged. Furthermore, in a case where aplurality of semiconductor laser diodes are used, a video image of highbrightness can be realized by collecting a low power laser diodes.

BRIEF DESCRIPTION OF THE DRAWINGS

The above features and advantages of the present invention will becomemore apparent by describing in detail exemplary embodiments thereof withreference to the attached drawings in which:

FIG. 1 is a schematic view of the configuration of a laser videoprojector according to the prior art;

FIG. 2 is a plan view of the configuration of an optical engine of thelaser video projector shown in FIG. 1;

FIG. 3 is a schematic view of a laser video projector according to afirst embodiment of the present invention;

FIGS. 4 and 5 are detailed views for respectively explaining a methodfor separating laser light using a monochromatic separator included inthe laser video projector shown in FIG. 3, according to an embodiment ofthe present invention;

FIG. 6 is an extended view of a multi-channel acousto-optic modulator inthe laser video projector shown in FIG. 3;

FIG. 7 is a plan view of a multi-channel acousto-optic modulator in thelaser video projector shown in FIG. 3 according to an embodiment of thepresent invention;

FIG. 8 is a perspective view of a modified optical scanner in the laservideo projector shown in FIG. 3;

FIG. 9 is a schematic view of a laser video projector according to anembodiment of the present invention;

FIG. 10 is a cross-sectional view of the configuration of a laser videoprojector according to an embodiment of the present invention;

FIG. 11 is a plan view of the arrangement stages on which optical fibersare arranged in the laser video projector according to an embodiment ofthe present invention;

FIG. 12 is a cross-sectional view taken along line 12-12′ of FIG. 11;

FIG. 13 is a circuit diagram illustrating circuit and method for drivingthe laser video projector shown in FIGS. 3, 9, and 10; and

FIG. 14 is a view illustrating write/read clock signals applied tochannels in the block diagram shown in FIG. 13.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, a laser video projector according to embodiments of thepresent invention, and a method and circuit for driving the same will bedescribed in detail with reference to the attached drawings. In thedrawings, the thicknesses of layers or regions are exaggerated forclarity.

First, the laser video projector according to the embodiments of thepresent invention will be described. Here, since two or more lines arescanned on a screen at the same time, an optic modulator may include atleast six or more channels. However, let us assume that four lines arescanned on a screen at the same time and the optic modulator includestwelve channels.

As shown in FIG. 3, a laser video projector according to an embodimentof the present invention includes a light generating portion P1, anoptic modulator P2, a light combining portion P3, and an optic scanningportion P4. The light generating portion generates red, green, and bluelight beams R, G, and B that will be used for displaying a video imagefrom an external input by the light modulation process. The lightgenerating portion P1 generates as many light beams as the number ofscan lines to be scanned on a screen 90 at the same time. For example,if there are 4 scan lines to be scanned on the screen 90 at the sametime, the light generating portion P1 generates four red light beams,four green light beams, and four blue light beams at the same time.Then, the red, green, and blue video signals R, G, and B separated asmany as scan lines (at least two or more) to be scanned at the same timeare input to the optic modulator P2. The optic modulator P2 modulates aplurality of red light beams, a plurality of green light beams, and aplurality of blue light beams, at the same time, which are incident fromthe light generating portion P1 and are focused, using the red, green,and blue video signals R, G, and B. Also, the light combining portion P3combines the plurality of red light beams, the plurality of green lightbeams, and the plurality of blue light beams in a predetermined order.For example, in a case where the plurality of red light beams are firstthrough fourth red light beams, the plurality of green light beams arefirst through fourth light beams, and the plurality of blue light beamsare first through fourth light beams, the light combining portion P3respectively combines the first red, green, and blue light beams, thesecond red, green, and blue light beams, the third red, green, and bluelight beams, and the fourth red, green, and blue light beams. Then, theoptic scanning portion P4 scans the combined light beams on the screen90.

The light generating portion P1 includes a light source 10 to make avideo image, first and second optical path changing portions 21 and 69a, and first and second optical transmission/reflection portions 67 aand 68 a. The first and second optical path changing portions 21 and 69a reflect incident light to change optical paths. The first and secondtransmission/reflection portions 67 a and 68 a transmit a portion of theincident light and reflect other portions of the incident light. Thelight source 10 may be a gas laser emitting white laser light as a laserlight source, a gas laser emitting red, green, and blue laser lightbeams R, G, and B, a solid state laser using a wavelength conversionmethod, or a semiconductor laser diode. It is preferable that the firstand second optical changing portions 21 and 69 a are first and secondhigh reflection mirrors. However, the first and second optical changingportions 21 and 69 a may be replaced with optical elements that canperform the same function. It is preferable that the first and secondtransmission/reflection portions 67 a and 68 a are first and seconddichroic mirrors. In an event that the emitted laser light L_(R+G+B) isa white laser light into which red, green, and blue laser light beamsare combined, a chromatic correction lens may be used as a collimatinglens that collimates laser light L_(R+G+B) emitted between the lightsource 10 and the first optical path changing portion 21.

The light generating portion P1 includes first, second, and thirdmonochromatic separators 26, 27, and 28 which separates incidentmonochromatic light, e.g., red light R, green light G, or blue light R,into as many laser light beams, having the same optical power, as thescan lines to be scanned on the screen 900 at the same time.

FIGS. 4 and 5 shows respectively embodiments of the first, second, andthird monochromatic separators 26, 27, and 28. As seen in FIG. 4, eachof the first, second, and third monochromatic separators 26, 27, and 28may be a transmissible (transparent) plate P that includes a firstanti-reflection coating film R1, first, second, and third highreflection coating films R2, R3, and R4, first, second, and thirdtransmission/reflection films R5, R6, and R7, and a secondanti-reflection coating film R8. The first anti-reflection coating filmR1 transmits more than 99% of light incident on a surface on which themonochromatic light is incident. The first, second, and third highreflection coating films R2, R3, and R4 reflect more than 99% ofincident light. The first, second, and third transmission/reflectionfilms R5, R6, and R7 have a predetermined transmissivity and reflectanceto transmit a portion of light incident on a surface from which themonochromatic light is emitted and reflect other portions of the light.The second anti-reflection coating film R8 transmits more than 99% ofthe light reflected by the third high reflection coating film R4.

As described above, it is preferable that the first, second, and thirdmonochromatic separators 26, 27, and 28 separate incident monochromaticlight into a plurality of light beams having the same optical power. Themonochromatic light is substantially separated by the first, second, andthird transmission/reflection films R5, R6, and R7 in the first, second,and third monochromatic separators 26, 27, and 28. Thus, it ispreferable that the first, second, and third transmission/reflectionfilms R5, R6, and R7 equally separate the monochromatic light.

In detail, it is preferable that the first transmission/reflection filmR5 has a transmissivity of about 25% and a reflectance of about 75% toseparate monochromatic light passing through the first anti-reflectioncoating film R1, i.e., ¼ of red laser light, green laser light, or bluelaser light. The second transmission/reflection film R6 faces the firstreflection coating film R2 on which 75% (¾) of the monochromatic lightis incident from the first transmission/reflection film R5. The secondtransmission/reflection film R6 transmits ⅓ of 75% (¾) of themonochromatic light incident from the first high reflection coating filmR2 and reflects the remaining portions (¾*⅔= 6/12=½, 50%) to the secondhigh reflection coating film R3. Thus, it is preferable that the secondtransmission/reflection film R6 has a transmissivity of 33% and areflectance of 66.7%. The third transmission/reflection film R7transmits 25% corresponding to ½ of 50% of the monochromatic lightincident from the second high reflection coating film R3 facing thethird transmission/reflection film R7. Thus, it is preferable that thethird transmission/reflection film R7 has a transmissivity of 50% and areflectance of 50%. It is preferable that the first, second, and thirdtransmission/reflection films R5, R6, and R7 are multi-layered coatingfilms to have different transmissivities and reflectances.

At least one or more transmission/reflection films that adjust thetransmissivity to a separation ratio of the monochromatic light and ananti-reflection coating film having a transmissivity of more than 99%may be placed on a second surface of the transparent plate P. Thus, themonochromatic light may be separated into at least two or moremonochromatic light beams having the same optical power.

As shown in FIG. 5, each of the first, second, and third monochromaticseparators 26, 27, and 28 may include first, second, and third beamsplitters BS1, BS2, and BS3 and a high reflection mirror HM having areflectance of more than 99%. It is preferable that the first beamsplitter BS1 reflects about 75% of the monochromatic light to the secondbeam splitter BS2 and transmits about 25% of the monochromatic light. Itis preferable that the second beam splitter BS2 reflects about 33.3% of75% light incident from the first beam splitter BS1 and transmits about66.7% of 75% light. It is preferable that the third beam splitter BS3reflects 50% of 66.7% light (corresponding to 50% of the monochromaticlight) incident from the second beam splitter BS2 and transmits 50% of66.7% light. It is preferable that the high reflection mirror HMreflects more than 99% of 50% light (corresponding to 25% of themonochromatic light) incident from the third beam splitter BS3. As aresult, four light beams having the same optical power are obtained fromthe first, second, and third beam splitters BS1, BS2, and BS3 and thehigh reflection mirror HM.

Even in a case where each of the first, second, and third monochromaticseparators 26, 27, and 28 includes beam splitters and a high reflectionmirror, by using at least one or more beam splitters that adjust thetransmissivity to a separation ratio of the monochromatic light and onehigh reflection mirror having a reflectance of more than 99%, themonochromatic light may be separated into at least two or moremonochromatic light beams having the same optical power.

The light generating portion P1 includes first, second, and third groupsof lenses 64 a, 65 a, and 66 a that are placed between the first,second, and third monochromatic separators 26, 27, and 28 and the opticmodulator P2 and focus light beams incident from the first, second, andthird monochromatic separators 26, 27, and 28 on the optic modulator P2.The first, second, and third groups of lenses 64, 65 a, and 66 a includefirst, second, third, and fourth micro lenses L1, L2, L3, and L4, fifth,sixth, seventh, and eighth micro lenses L5, L6, L7, and L8, and ninth,tenth, eleventh, and twelfth micro lenses L9, L10, L10, and L12. Thefirst monochromatic separator 26 separates red laser light into first,second, third, and fourth red laser light beams L_(R1), L_(R2), L_(R3),and L_(R4). The second monochromatic separator 27 separates green laserlight into first, second, third, and fourth green laser light beamsL_(G1), L_(G2), L_(G3), and L_(G4). The third monochromatic separator 28separates blue laser light into first, second, third, and fourth bluelaser light beams L_(B1), L_(B2), L_(B3), and L_(B4). Thus, the first,second, third, and fourth red laser light beams L_(R1), L_(R2), L_(R3),and L_(R4), the first, second, third, and fourth green laser light beamsL_(G1), L_(G2), L_(G3), and L_(G4), and the first, second, third, andfourth blue laser light beams L_(B1), L_(B2), L_(B3), and L_(B4)correspond on an one-to-one basis to the first through twelfth microlenses L1 through L12 and are focused on the optic modulator P2.

Describing the optical path of light in the light generating portion P1,laser light L_(R+G+B) emitted from the light source 10 is reflected tothe first light transmission/reflection portion 67 a by the firstoptical path changing portion 21. Colors of the laser light emitted fromthe first light transmission/reflection portion 67 a are separated. Aportion (a blue laser light beam L_(B)) of the laser light L_(R+G+B) isreflected to the third monochromatic separator 28 and the other portions(red and green laser light beam L_(R+G)) of the laser light L_(R+G+B)are transmitted to the second light transmission/reflection portion 68a. The second light transmission/reflection portion 68 a separates thered and green laser light beam L_(R+G). In this process, the green laserlight beam L_(G) is reflected to the second monochromatic separator 27and the red laser light beam L_(R) is transmitted to the second opticalchanging portion 69 a. The red laser light beam L_(R) is reflected tothe first monochromatic separator 26 by the second optical path changingportion 69 a. The monochromatic light incident on first, second, andthird monochromatic separators 26, 27, and 28, i.e., each of red, green,and blue laser light beams L_(R), L_(G), and L_(B), is separated in asmany beams as the scan lines scanned on the screen 90 at the same time.For example, in a case where four scan lines are scanned on the screen90 at the same time, the red, green, and blue laser light beams L_(R),L_(G), and L_(B) are separated into first, second, third, and fourthred, green, and blue laser light beams L_(R1), L_(R2), L_(R3), andL_(R4), L_(G1), L_(G2), L_(G3), and L_(G4), and L_(B1), L_(B2), L_(B3),and L_(B4) by the first, second, and third monochromatic separators 26,27, and 28. The first, second, third, and fourth red laser light beamsL_(R1), L_(R2), L_(R3), and L_(R4) are focused on the optic modulator P2via the ninth, tenth, eleventh, and twelfth micro lenses L9, L10, L11,and L12 of the third group of lenses 66 a. The first, second, third, andfourth green laser light beams L_(G1), L_(G2), L_(G3), and L_(G4) arefocused on the optic modulator P2 via the fifth, sixth, seventh, andeighth micro lenses L5, L6, L7, and L8 of the second group of lenses 65a. The first, second, third, and fourth blue laser light beams L_(B1),L_(B2), L_(B3), and L_(B4) are focused on the optic modulator P2 via thefirst, second, third, and fourth micro lenses L1, L2, L3, and L4 of thefirst group of lenses 64 a.

The optic modulator P2 includes first, second, and third multi-channelacousto-optic modulators 63, 62, and 61. The first multi-channelacousto-optic modulator 63 modulates the first, second, third, andfourth red laser light beams L_(R1), L_(R2), L_(R3), and L_(R4) at thesame time. The second multi-channel acousto-optic modulator 62 modulatesthe first, second, third, and fourth green laser light beams L_(G1),L_(G2), L_(G3), and L_(G4) at the same time. The third multi-channelacousto-optic modulator 61 modulates the first, second, third, andfourth L_(B1), L_(B2), L_(B3), and L_(B4) at the same time. FIG. 6 is anenlarged perspective view of one of the first, second, and thirdmulti-channel acousto-optic modulators 63, 62, and 61. Each of thefirst, second, and third multi-channel acousto-optic modulators 63, 62,and 61 has four optic modulation channels ch1, ch2, ch3, and ch4 thatare made of an optical monocrystalline medium such as tellurium dioxide(TeO₂). First, second, third, and fourth transducers T1, T2, T3, and T4exist on the optic modulation channels ch1, ch2, ch3, and ch4. First,second, third, and fourth electrodes E1, E2, E3, and E4, to which videosignals are applied at the same time to be modulated, exist on the firstthrough fourth T1, T2, T3, and T4 transducers. It is preferable that thefirst, second, third, and fourth transducers T1, T2, T3, T4 are LiNbO₃monocrystalline thin films. It is preferable that the first throughfourth electrodes E1 through E4 are formed of metal thin films.Reference character C denotes cuts to a predetermined depth in the opticmodulation channels ch1, ch2, ch3, and ch4 of each of the first, second,and third multi-channel acousto-optic modulators 63, 62, and 61. Thecuts C are to prevent crosstalk among the optic modulation channels ch1,ch2, ch3, and ch4 during the optical modulation process. A scratchpattern SC to prevent ultrasonic waves generated by the optic modulationchannels ch1, ch2, ch3, and ch4 from being reflected is formed to asurface facing the first, second, third, and fourth electrodes E1, E2,E3, and E4 of each of the first, second, and third multi-channelacousto-optic modulators 63, 62, and 61. Alternatively, a material forabsorbing the ultrasonic waves may exist on the surface instead of thescratch pattern SC.

In order to modulate the laser light beams incident on the opticmodulator P2 at the same time, each of the first, second, and thirdmulti-channel acousto-optic modulators 63, 62, and 61 has four opticmodulation channels, a number identical to the number of the scan linesscanned on the screen 90 at the same time. For example, the firstmulti-channel acousto-optic modulator 63 has first through fourth opticmodulation channels to modulate the first, second, third, and fourthlaser light beams L_(R1), L_(R2), L_(R3), and L_(R4) at the same time.

The simultaneous modulation of laser light beams incident on the first,second, and third multi-channel acousto-optic modulators 63, 62, and 61is achieved by color video signals applied to the first, second, andthird multi-channel acousto-optic modulators 63, 62, and 61. In otherwords, when the first, second, third, and fourth red laser light beamsL_(R1), L_(R2), L_(R3), and L_(R4) are focused on the first throughfourth optic modulation channels of the first multi-channelacousto-optic modulator 63, red video signals are applied to the firstthrough fourth optic modulation channels. Thus, the first, second,third, and fourth red laser light beams L_(R1), L_(R2), L_(R3), andL_(R4) passing through the first through fourth optic modulationchannels are modulated at the same time. The first, second, third, andfourth green laser light beams L_(G1), L_(G2), L_(G3), and L_(G4) andthe first, second, third, and fourth blue laser light beams L_(B1),L_(B2), L_(B3), and L_(B4) are modulated using the same modulationprocess except the different color video signals.

Instead of the first, second, and third multi-channel acousto-opticmodulators 63, 62, and 61, the optic modulator P2 may include onemulti-channel acousto-optic modulator having all of optic modulationchannels of the first, second, and third multi-channel acousto-opticmodulators 63, 62, and 61.

FIG. 7 illustrates a multi-channel optic modulator P2 a having firstthrough twelfth channels ch1′ through ch12′. The first through fourthchannels ch1′ through ch4′ of the first through twelfth channels ch1′through ch12′ modulate the first, second, third, and fourth red laserlight beams L_(R1), L_(R2), L_(R3), and L_(R4). The fifth through eighthchannels ch5′ through ch8′ modulate the first, second, third, and fourthgreen laser light beams L_(G1), L_(G2), L_(G3), and L_(G4). The ninththrough twelfth channels ch9′ through ch12′ modulate the first, second,third, and fourth blue laser light beams L_(B1), L_(B2), L_(B3), andL_(B4). When laser light beams to be modulated are applied to the firstthrough twelfth channels ch1′ through ch12′, red video signals aresimultaneously applied to electrodes E1′, E2′, E3′, and E4′ of the firstthrough fourth channels ch1′ through ch4′, green video signals aresimultaneously applied to the fifth through eighth channels ch5′ throughch8′, and blue video signals are simultaneously applied to the ninththrough twelfth channels ch9′ through ch12′. Reference characters C1through C11 denote cuts to a predetermined depth in the first throughtwelfth channels ch1′ through ch12′, respectively. Reference charactersT1 through T12 denote first through twelfth transducers and E1′ throughE12′ denote first through twelfth electrodes.

The optic combining portion P3, in which modulated laser light beamsthat pass through the channels of the optic modulator P2 using theapplied video signals are combined, includes fourth, fifth, and sixthgroups of lenses 64 b, 65 b, and 66 b, the third optical path changingportion 67 b, the third light transmission/reflection portion 68 b, andthe fourth light transmission/reflection portion 69 b. The fourth,fifth, and sixth groups of lenses 64 b, 65 b, and 66 b one-to-onecorrespond to the first, second, and third multi-channel acousto-opticmodulators 63, 62, and 61 of the optic modulator P2. The third opticalpath changing portion 67 b reflects blue laser light beams L_(B1)′,L_(B2)′, L_(B3)′, and L_(B4)′, which are modulated and incident from thefourth group of lenses 64 b, toward the optic scanning portion P4. Thethird light transmission/reflection portion 68 b reflects green laserlight beams L_(G1)′, L_(G2)′, L_(G3)′, and L_(G4)′, which are modulatedand incident from the fifth group of lenses 65 b, toward the opticscanning portion P4 and transmits the blue laser light beams L_(B1)′,L_(B2)′, L_(B3)′, and L_(B4)′ incident from the third optical pathchanging portion 67 b. The fourth light transmission/reflection portion69 b reflects red laser light beams L_(R1)′, L_(R2)′, L_(R3)′, andL_(R4)′, which are modulated and incident from the sixth group of lenses66 b, toward the optic scanning portion P4 and transmits laser lightbeams L_(R1)′+L_(B1)′, L_(R2)′+L_(B2)′, L_(R3)′+L_(B3)′, andL_(R4)′+L_(B4)′ incident form the third light transmission/reflectionportion 68 b.

The third optical path changing portion 67 b is the third highreflection mirror. The third and fourth light transmission/reflectionportions 68 b and 69 b are respectively the third dichroic mirror, whichhas very low transmissivity with respect to green light and very hightransmissivity with respect to blue light and the fourth dichroicmirror, which has very low transmissivity with respect to red light andvery high transmissivity with respect to green light and red light. Thefourth, fifth, and sixth groups of lenses 64 b, 65 b, and 66 b changelaser light beams incident form the optic modulator P2 to parallel laserlight beams. For this, each of the fourth, fifth, and sixth groups oflenses 64 b, 65 b, and 66 b includes four micro lenses. Thirteenththrough sixteenth micro lenses L13 through L16 of the fourth group oflenses 64 b one-to-one correspond to four channels of the thirdmulti-channel acousto-optic modulator 61. Seventeenth through twentiethmicro lenses L17 through L20 of the fifth group of lenses 65 bcorrespond on a one-to-one basis to four channels of the secondmulti-channel acousto-optic modulator 62. Twenty first through twentyfourth micro lenses L21 through L24 of the sixth group of lenses 66 bcorrespond on a one-to-one basis to four channels of the firstmulti-channel acousto-optic modulator 63.

The optical paths of modulated laser light beams incident from the opticmodulator P2 to the optic combining portion P3, modulated red, green,and blue laser light beams L_(R1)′, L_(R2)′, L_(R3)′, and L_(R4)′,L_(G1)′, L_(G2)′, L_(G3)′, and L_(G4)′, and L_(B1)′, L_(B2)′, L_(B3)′,and L_(B4)′ incident from twelve channels of the first, second, andthird multi-channel acousto-optic modulators 63, 62, and 61 are changedto parallel laser light beams via twelve micro lenses L24, L23, . . .L14, and L13 of the sixth, fifth, and fourth groups of lenses 66 b, 65b, and 64 b. The modulated blue laser light beams L_(B1)′, L_(B2)′,L_(B3)′, and L_(B4)′ passing through the thirteenth through sixteenthmicro lenses L13 through L16 of the fourth group of lenses 64 b arereflected by the third optical path changing portion 67 b andtransmitted to the optic scanning portion P4 through the third andfourth light transmission/reflection portions 68 b and 69 b. In thisprocess, the modulated blue laser light beams L_(B1)′, L_(B2)′, L_(B3)′,and L_(B4)′ are respectively combined with modulated green laser lightbeams L_(G1)′, L_(G2)′, L_(G3)′, and L_(G4)′ which are transmittedthrough the third light transmission/reflection portion 68 b andreflected to the fourth light transmission/reflection portion 69 b bythe third light transmission/reflection portion 68 b. The combined laserlight beams L_(G1)′+L_(B1)′, L_(G2)′+L_(B2)′, L_(G3)′+L_(B3)′, andL_(G4)′+L_(B4)′ are combined with modulated red laser light beamsL_(R1)′, L_(R2)′, L_(R3)′, and L_(R4)′, which are transmitted throughthe fourth light transmission/reflection portion 69 b and reflected tothe optic scanning portion P4 by the fourth lighttransmission/reflection portion 69 b. The combined laser light beamsL_(R1)′+L_(G1)′+L_(B1)′, L_(R2)′+L_(G2)′+L_(B2)′,L_(R3)′+L_(G3)′+L_(B3)′, and L_(G4)′+L_(G4)′+L_(B4)′ correspond to onescan line, containing red, green, and blue colors, scanned on the screen90. Thus, four combined laser light beams L_(R1)′+L_(G1)′+L_(B1)′,L_(R2)′+L_(G2)′+L_(B2)′, L_(R3)′+L_(G3)′+L_(B3)′, andL_(G4)′+L_(G4)′+L_(B4)′ corresponding to four scan lines aresimultaneously incident on the optic scanning portion P4 from the opticcombining portion P3.

The optic scanning portion P4 includes a first focusing lens 71, a firstscanner 70, second scanner 80, a first relay lens RL1, a second relaylens RL2, and a second focusing lens 72. The first focusing lens 71focuses four combined laser light beams L_(R1)′+L_(G1)′+L_(B1)′,L_(R2)′+L_(G2)′+L_(B2)′, L_(R3)′+L_(G3)′+L_(B3)′, andL_(R4)′+L_(G4)′+L_(B4)′. The first scanner 70 periodically reflectslight focused by the first focusing lens 71 to horizontally scan thefocused light on the screen 90. The second scanner 80 scans the lightincident from the first scanner 71 on the screen 90 and determines thevertical position of the incident light to be scanned. The first andsecond relay lenses RL1 and RL2 are positioned in an optical pathbetween the first and second scanners 70 and 80 so that the lightreflected by the first scanner 70 is focused on the second scanner 80.The second focusing lens 72 is placed between the screen 90 and thesecond scanner 80 to control distances among a plurality of scan linesthat are scanned on the screen 90 from the second scanner 80. Referencecharacter SL denotes the scan lines.

The first and second relay lenses RL1 and RL2 focus the horizontallyscanned light by the first scanner 70 so that the horizontally scannedlight is incident within a range of the effective area of the secondscanner 80 to be vertically scanned. It is preferable that the firstscanner 70 is a polygon mirror and the second scanner 80 is agalvanometer. However, the first and second scanners 70 and 80 may bereplaced with optical elements that perform the same function. It ispreferable that the first and second focusing lenses 71 and 72 and thefirst and second relay lenses RL1 and RL2 are convex lenses.

As shown in FIG. 8, the optic scanning portion P4 may include first andsecond scanners 70 and 80, first and second relay lenses RL1 and RL2,and a reflector plate RP that projects light incident from the secondscanner 80 toward the screen 90 above the second scanner 80.

In a laser video projector according to a second embodiment, a lightsource portion includes a plurality of first light sources emitting redlaser light, a plurality of second light sources emitting green laserlight, and a plurality of third light sources emitting blue laser light.Light is transmitted from the light source portion to an opticmodulator. The modulated light is transmitted from the optic modulatorto an optic scanning portion using optical fibers. Thus, the laser videoprojector according to the second embodiment of the present invention isdifferent from the laser video projector according to the firstembodiment of the present invention in that its size is reduced.

The same elements of the laser video projector according to the secondembodiment of the present invention as those of the laser videoprojector according to the first embodiment of the present invention areassigned identical reference numerals (characters). Thus, thedescriptions of these elements will not be repeated here.

Referring to FIG. 9, the laser video projector according to the secondembodiment of the present invention includes a light generating portionP5, an optic modulator P2, an optic combining portion P6, an opticscanning portion P4, and a screen 90. The light generating portion P5generates light to be used to project a video image, e.g., laser light.The optic modulator P2 modulates light generated by the light generatingportion P5. The optic combining portion P6 combines light beams emittedfrom the optic modulator P2 via predetermined channels. The opticscanning portion P4 scans the combined light beams on the screen 90 todisplay a video image.

The light generating portion P5 includes first through fourth lightsources LD1 through LD4 emitting red laser light, fifth through eighthlight sources LD5 through LD8 emitting green laser light, and ninththrough twelfth light sources LD9 through LD12 emitting blue laserlight. The light generating portion P5 also includes twelve opticalfibers OF1 through OF12 corresponding on a one-to-one basis to the firstthrough twelfth light sources LD1 through LD12 to transmit monochromaticlaser light beams emitted from the first through twelfth light sourcesLD1 through LD12 to the optic modulator P2. First micro focusing lensesFL1 correspond on a one-to-one basis to the first through twelfthoptical fibers OF1 through OF12 to focus monochromatic light beamsemitted to the other ends of the optical fibers OF1 through OF12 on apredetermined position of the optic modulator P2. The first microfocusing lenses FL1 correspond on a one-to-one basis to twelve channelsof first, second, and third multi-channel acousto-optic modulators 63,62, and 61 of the optic modulator P2. Thus, four red light beams, fourgreen light beams, and four blue light beams emitted from the firstthrough twelfth light sources LD1 through LD12 are transmitted near tothe optic modulator P2 via the optical fibers OF1 through OF12 and thenfocused on twelve channels of the optic modulator P2 by the firstfocusing lenses FL1.

As described above, the first micro focusing lenses FL1 perform the samefunctions as the first, second, and third groups of lenses 64 a, 65 a,and 66 a. By using the first micro focusing lenses FL1, the size of thelaser video projector can be greatly reduced.

A process of modulating, the red, green, and blue light beams focused onthe optic modulator P2 is identical to the process described in theprevious embodiment. As in the previous embodiment, the optic modulatorP2 may include one multi-channel acousto-optic modulator having twelveoptic modulation channels shown in FIG. 7.

In the optic modulator P5 having the above-described structure, it ispreferable that the first through twelfth light sources LD1 through LD12are semiconductor laser diodes that are formed using a semiconductormanufacturing process. However, the first through twelfth light sourcesLD1 through LD12 may be different types of laser diodes that emit red,green, and blue laser light beams to be used to project a video image.

The semiconductor laser diodes or optical fibers have a size smallerthan the first and second optical path changing portions 21 and 69 a,the first and second light transmission/reflection portions 67 a and 68a, and the first, second, and third monochromatic separators 26, 27, and28 described in the previous embodiment. The laser video projectoraccording to the present embodiment is smaller than the laser videoprojector according to the previous embodiment.

The optic combining portion P6 includes second micro focusing lenses FL2corresponding on a one-to-one basis to twelve channels of the opticmodulator P2 to focus modulate red, green, and blue laser light beamsemitted from the channels of the optic modulator P2. The optic combiningportion P6 also includes twelve optical fibers OF12 through OF24 totransmit modulated laser light beams emitted from the optic modulator P2to the optic scanning portion P4. The thirteenth through sixteenthoptical fibers OF13 through OF16 transmit modulated red laser lightbeams, the seventeenth through twentieth optical fibers OF17 throughOF20 transmit modulated green laser light beams, and the twenty firstthrough twenty fourth optical fibers OF21 through FO24 transmitmodulated blue laser light beams. The second micro focusing lenses FL2are attached to respective ends of the thirteenth through twenty fourthoptical fibers OF13 through OF24 which receive the modulated red, green,and blue laser light beams. While advancing toward the optic scanningportion P4, the twelve optical fibers OF13 through 24 are combined intofour optical fibers COF1, COF2, COF3, and COF4. In other words, thethirteenth, seventeenth, and twenty first optical fibers OF13, OF17, andOF21 are combined into the first optical fiber COF1. The fourteenth,eighteenth, and twenty second optical fibers OF14, OF18, and OF22 arecombined into the second optical fiber COF2. The fifteenth, nineteenth,and twenty third optical fibers OF15, OF19, and OF23 are combined intothe third optical fiber COF3. The sixteenth, twentieth, and twentyfourth optical fibers OF16, OF20, and OF24 are combined into the fourthoptical fiber COF4. Ends of the first through fourth optical fibers COF1through COF4 are polished in order to attach lenses to the ends. Threeoptical fibers of each of the first through fourth optical fibers COF1through COF4 are optical paths through which modulated red, green, andblue laser light beams are transmitted from the optic modulator P2 usingvideo signals. Thus, laser light beams transmitted through the firstthrough fourth optical fibers COF1 through COF4 are combined with laserlight beams containing the modulated red, green, and blue laser lightbeams. The first through fourth optical fibers COF1 through COF4 arechannels through which videos including red, green, and blue videosignals, mixed in a predetermined ratio to be scanned on a screen aretransmitted. In other words, the first through fourth optical fibersCOF1 through COF4 are channels through which videos to be scanned on thescreen 90 are transmitted. Laser light beams transmitted through thefirst through fourth optical fibers COF1 through COF4 are simultaneouslyscanned on the screen 90 via the optic modulator P4 presented in thefirst embodiment. Thus, four scan lines are scanned on the screen 90 atthe same time. The resolution of a video image projected on the screen90 increases as much as the number of scan lines simultaneously scannedon screen 90. In the present invention, the resolution of a video canincrease four times compared with the prior art. Third micro focusinglenses FL3 are attached to ends of the first through fourth opticalfibers COF1 through COF4. Due to the third micro focusing lenses FL3,laser light beams transmitted through the first through fourth opticalfibers COF1 through COF4 are parallel incident on the first focusinglens 71 of the optic scanning portion P4 via the third micro focusinglenses FL3. A process of scanning the incident laser light beams on thescreen 90 via the optic scanning portion P4 is the same as thatdescribed in the previous embodiment.

A laser video projector according to another embodiment has a structuresimpler than the laser video projector according to the secondembodiment because a light generating portion does not have opticalfibers. The laser video projector according to the present inventionincludes an optic modulator, an optic combining portion, and an opticscanning portion, the structures of which are the same as those of theoptic modulator, the optic combining portion, and the optic scanningportion described in the first part of the description of the presentinvention. Thus, only the light generating portion will be described inthis embodiment. Also, in the drawings, the optic modulator, the opticcombining portion, and the optic scanning portion are represented asblocks and a screen of the projector is not shown.

In detail, referring to FIG. 10, a light generating portion P7 of thelaser video projector according to a third embodiment of the presentinvention includes a light source portion 920 and seventh, eighth, andninth groups of lenses 64 c, 65 c, and 66 c. The light source portion920 emits red laser light, green laser light, and blue laser light. Theseventh, eighth, and ninth groups of lenses 64 c, 65 c, and 66 c areclose to the optic modulator P2 to focus laser light beams emitted fromthe light source portion 920 on channels of the optic modulator P2. Likethe light source portion 910 described in the previous embodiment, thelight source portion 920 includes four red laser emitting sources 920 a,920 b, 920 c, and 920 d, four green laser emitting sources 920 e, 920 f,920 g, and 920 h, and four blue laser emitting sources 920 i, 920 j, 920k, and 920 l. It is preferable that the red, green, and blue laseremitting sources 920 a through 920 l are semiconductor laser diodes. Theseventh, eighth, and ninth groups of lenses 64 c, 65 c, and 66 c areequal to the first, second, and third groups of lenses 64 a, 65 a, and66 a described in the first embodiment. In other words, the seventh,eighth, and ninth groups of lenses 64 c, 65 c, and 66 c have twelvemicro lenses L1 through L12. The twelve micro lenses L1 through L12correspond on a one-to-one basis to the red, green, and blue laseremitting sources 920 a through 920 l constituting the light sourceportion 920. It is preferable that the laser emitting sources 920 athrough 920 l are close to the micro lenses L1 through L12 to increasethe efficiency for focusing red, green, and blue laser light beamsemitted from the laser emitting sources 920 a through 920 l on twelvechannels of the optic modulator P2 via the micro lenses L1 through L12.

In the previous and present embodiments, the optical fibers of the opticmodulator P5 or P7 or the optical fibers OF13 through OF24 of the opticcombiner P6 and the first through fourth optical fibers COF1 throughCOF4 may be linear or curvilinear. However, it is preferable that theoptical fibers of the optic modulator P5 or P7 or the optical fibersOF13 through OF24 of the optic combiner P6 and the first through fourthoptical fibers COF1 through COF4 are constituted so that laser lightbeams emitted from the optical fibers are accurately focused onpredetermined channels of the optic modulator P2 and modulated laserlight beams emitted from the channels of the optic modulator P2 areaccurately focused on predetermined optical fibers of the optic combinerP6. For this, as shown in FIG. 11, the laser video projector accordingto the previous embodiment may further include first, second, and thirdarrangement stages S1, S2, and S3 for arranging twelve optical fibersOF1 through OF12 of the light generating portion P5, twelve opticalfibers OF13 through OF24 of the optic combining portion P6, and fouroptical fibers COF1 through COF4. In this case, on the first, second,and third arrangement stages S1, S2, and S3, only minimum portions ofthe optical fibers may be arranged. For example, as on a first virtualarrangement state FS1, on the first arrangement state S1, onlypredetermined lengths of the total lengths of the optical fibers OF1through OF12, including portions to which the first micro focusinglenses FL1 are attached, may be arranged. As on a second virtualarrangement state FS2, on the second arrangement state S2, onlypredetermined lengths of the total lengths of the optical fibers OF13through OF24, including portions to which the second micro focusinglenses FL2 are attached, may be arranged. As on a third virtualarrangement stage FS3, on the third arrangement stage S3, onlypredetermined lengths of the total lengths of the first through fourthoptical fibers COF1 through COF4, including portions to which the thirdmicro focusing lenses FS3 are attached, may be arranged.

FIG. 12 is a cross-sectional view taken along line 12-12′ of FIG. 11.Referring to FIG. 12, on the surface of the first arrangement state S1,a plurality of V-shaped grooves G are formed to arrange the opticalfibers OF1 through OF12 therein. The cross-section of the firstarrangement stage S1 may be used to describe cross-sections of thesecond and third arrangement stages S2 and S3.

In the laser video projector, the resolution of a video image projectedon the screen 90 depends on the horizontally scanning speed of the firstoptic scanner 70 and video processing speeds of the first, second, andthird multi-channel acousto-optic modulators 63, 62, and 61. When videosignals are processed at the same time by using the first, second, andthird multi-channel acousto-optic modulators 63, 62, and 61 each havingfour channels, each of the first, second, and third multi-channelacousto-optic modulators 63, 62, and 61 processes video signals at aspeed of ¼ times. Also, since the optic scanner 70 scans four scan linesat the same time, the first optic scanner 70 should be driven at ascanning speed corresponding to ¼ of the speed for scanning one scanline. The video processing speeds can be adjusted by dividing ahorizontal synchronization signal into 4 signals and then applying thedivided horizontal synchronization signals.

A method for driving the laser video projectors according to the firstthrough third embodiments will be described.

An analog signal input to a laser video projector is converted into adigital signal via an analog/digital (A/D) converter. The converteddigital signal is stored in a FIFO memory and then converted into ananalog signal via a digital/analog (D/A) converter. The converted analogsignal is applied to a drive for driving an optic modulator, and thuslaser light focused on the optic modulator is modulated. Here, if theoptic modulator is a multi-channel acousto-optic modulator having atleast two or more channels as described above, a video signal input viathe A/D converter is processed by using as many FIFO memories as thehorizontal scan lines to be simultaneously scanned and the D/Aconverter.

FIG. 13 is a circuit diagram illustrating a method and circuit fordriving the laser video projector according to the present invention.Here, each of the first, second, and third multi-channel acousto-opticmodulators 63, 62, and 61 has four optic modulation channels. In each ofthe first, second, and third multi-channel acousto-optic modulators 63,62, and 61 having four optic modulation channels, the same modulationprocess is performed. Thus, for convenience, FIG. 13 shows only aportion related to the first multi-channel acousto-optic modulator 63 onwhich red laser light is incident. Portions related to the second andthird multi-channel acousto-optic modulators 62 and 61 are shown assimple blocks.

Referring to FIG. 13, video signals R input to an A/D converter 930 arewritten in a memory having a plurality of FIFO memories. In other words,the video signals R are sequentially written in first, second, and thirdFIFO memories M1, M2, and M3 by using a horizontal synchronizationsignal Hs that is divided into four portions and then applied. Aftervideo signals corresponding to three scan lines are completely input tothe first, second, and third FIFO memories M1, M2, and M3, a videosignal corresponding to a fourth scan line is written in a fourth FIFOmemory M4, and simultaneously, video signals corresponding to four scanlines are read from the first, second, third, and fourth FIFO memoriesM1, M2, M3, and M4 at a speed that is four times lower than the speedfor inputting signals to the first, second, third, and fourth FIFOmemories M1, M2, M3, and M4. The read video signals are respectivelytransmitted to first, second, third, and fourth D/A converters 940 a,940 b, 940 c, and 940 d connected on a one-to-one basis to the first,second, third, and fourth FIFO memories M1, M2, M3, and M4. Thetransmitted video signals are simultaneously applied to four channelsch1, ch2, ch3, and ch4 in the first multi-channel acousto-opticmodulator 63. Thus, laser light beams simultaneously incident on thefour channels ch1, ch2, ch3, and ch4 from a light generating portion LSare modulated at the same time. The modulated laser light beams arescanned at a time on a screen by using an optic scanner so that a videoimage having a high resolution can be obtained.

FIG. 14 shows write clock signals used to store video information in thefirst, second, third, and fourth FIFO memories M1, M2, M3, and M4 and aread clock signal used to read video information from the first, second,third, and fourth M1, M2, M3 and M4 at the same time. Referencecharacters W1 through W4 denote first through fourth write clock signalssequentially applied to the first through fourth FIFO memories andreference character R denotes the read clock signal.

Referring to FIG. 14, the first through fourth write clock signals W1through W4 are sequentially generated in every ¼ cycle of the horizontalsynchronization signal Hs and sequentially applied to the first throughfourth FIFO memories. In this process, the read clock signal R isgenerated by the fourth write clock signal W4, lasts until first throughthird write clock signals W1 through W3 used for storing next videosignals are completely generated, and is read with the generation of anew fourth write clock signal W4. This means that video information iswritten in the first through third FIFO memories M1 through M3, and thenvideo information written in the first through fourth FIFO memories M1through M4 is read at the same time when video information is written inthe fourth FIFO memory M4.

As described above, in a laser video projector according to the presentinvention, a plurality of scan lines are simultaneously processed andscanned. Thus, an optic modulator's capability to process a video signaland the scanning speed of an optic scanner can be improved. Theresolution of video image projected in proportion to the number of opticmodulation channels can be constantly increased. Thus, limitations inthe performance of the optic modulator and the optic scanner can beovercome. The laser video projector can be made small by using laseremitting sources, optical fibers, and micro focusing lenses. Sincecomponents can be disposed in predetermined positions due to the opticalfibers, the degree of freedom for arranging the components increases.Also, since the optical fibers can be easily arranged by usingarrangement stages, the components can be well arranged. Furthermore, ina case where a plurality of semiconductor laser diodes are used, a videoimage of high brightness can be realized by collecting a low power laserdiodes.

The present invention has been particularly shown and described withreference to exemplary embodiments thereof. However, the embodiments ofthe present invention can be modified into various other forms, and thescope of the present invention must not be interpreted as beingrestricted to the embodiments. For example, it will be understood bythose of ordinary skill in the art that first through thirdmulti-channel acousto-optic modulators and optical fibers can bestacked, rather than being arranged in a line. In other words, after thefirst through third multi-channel acousto-optic modulators aresequentially stacked, four optical fibers each of twelve optical fiberscan be stacked. Moreover, in a laser video projector, a light generatingportion can be constituted according to a first embodiment of thepresent invention and an optic combining portion can be constitutedaccording to a second embodiment of the present invention or vice versa.Also, in the laser video projector, the light generating portion can beconstituted according to a third embodiment of the present invention andthe optic combining can be constituted according to the first or secondembodiment of the present invention. In addition, the laser videoprojector can be constituted, using a portion of elements of theconventional laser video projector shown in FIG. 1. Thus, the scope ofthe present invention must be defined by the appended claims not by theabove-described embodiments.

1. A method for driving a laser video projector including ananalog/digital converter that converts an analog video signal to adigital signal and a plurality of FIFO memories that are connected tothe analog/digital converter to write the digital signal, wherein videosignals read from the analog/digital converter are sequentially writtenin the plurality of FIFO memories, the video signals are read from theplurality of FIFO memories when a video signal is written in the lastone of the plurality of FIFO memories, and the analog video signal isone of R, G and B signals.
 2. The method of claim 1, wherein the videosignals are red video signals, green video signals, or blue videosignals.
 3. The method of claim 1, wherein the video signals are readfrom the plurality of FIFO memories at a speed lower than a speed forwriting the video signals in the plurality of FIFO memories.
 4. Acircuit for driving a laser video projector including an analog/digitalconverter that converts an analog signal to a digital signal, a memoryin which the analog signal is written, digital/analog converters thatconvert video information read from the memory to analog signals, and anoptic modulator that modulates light by using the analog signal readfrom the digital/analog converter, wherein the memory includes aplurality of FIFO memories in which video signals read from theanalog/digital converter are sequentially written, the number of thedigital/analog converters is equal to the number of the plurality ofFIFO memories, the optic modulator includes as many optic modulationchannels as the plurality of FIFO memories, the analog signal is one ofR, G and B signals, and the FIFO memories are connected to theanalog/digital converter.